As all of "Once Upon a Time" fans know already, "Frozen" is coming to Storybrooke. But there's still tons of information that we don't know of.

For one, the first two episode titles of "OUAT" season 4 has been released. Episode one is "The Tale of Two Sisters." The title of episode two was recently revealed by co-creator of the show Adam Horowitz via Twitter.

Horowitz tweeted: "Here's another #OnceUponATime #titlespoiler Hope to see ya 9/28 for Season 4!" He also shared a photo together with the tweet where you can see that the episode two title is "White Out." Needless to say, Horowitz confirmed the release date too as September 28. Jane Espensen wrote "White Out."

What could "White Out" be about? IBT speculates that this will be about how Elsa casts an eternal winter from where she came from, similar to the hit Disney movie. It is still unknown if Elsa in "OUAT" will be good or evil. But one thing's for sure, the main characters of the show will fight an evil force from the past, one that even Rumplestiltskin can't predict—The Ice Queen.

Some may think that Elsa could be The Ice Queen, or it could be someone else by the name of Elizabeth Mitchell. Mitchell was cast in early July and her role is not yet confirmed. Entertainment Weekly gave a few hints on what character Mitchell will play; they say it could be villainous. Could Mitchell possibly be the main villain in season 4?

On the other hand, cast members for the "Frozen" characters have been confirmed. Georgina Haig will play Elsa. Elizabeth Lail will play Anna. Scott Michael Foster will play Kristoff.

Discover the new world coming to "Once Upon a Time" season 4 on September 28.